The move requires the board to determine whether a new election should be held at the casino, which never recognized the original vote in March 2007 and refused to bargain. Its parent company, Trump Entertainment Resorts, claimed a pro-union rally held just before the vote and attended by local and state elected officials tainted the results.

That stance was rejected by the labor board, but the company is continuing to press an appeal in federal court.

Getting dealers to re-approve a union could be difficult in the current economic climate as Atlantic City's 11 casinos lose customers to slots parlors in Pennsylvania and New York.

The UAW also has been unable to reach a contract with Bally's Atlantic City, Caesars Atlantic City and the Tropicana Casino and Resort, and has authorized strikes at all three gambling halls. A walkout date has not been set.

It has spent heavily on a campaign targeting Bally's and Caesars in broadcast, print and billboard ads. The main slogan is, "When workers are treated unfairly, everyone loses at Bally's and Caesars."

Labor experts said employers facing unionization drives frequently try to prolong negotiations as long as possible in the hope workers will grow disenchanted with the union and eventually vote to get rid of it.

"Our disappointment is on the part of management's lack of cooperation with the law to sit down and bargain," said Mike Caplis, a 10-year Trump Plaza dealer who says he supports the union there.

To get the labor board to consider a decertification vote, at least 30 percent of workers must sign a petition.

The union was approved by a vote of 68 percent to 32 percent.

"This is that same 32 percent that voted against the union 2 1/2 years ago," Caplis said.

The UAW and Local 54 of UNITE HERE, the union representing hotel service workers, are bargaining with the casinos in the worst economic climate in the 31-year history of casino gambling here.

For the first eight months of this year, Atlantic City's revenue -- $2.7 billion -- is 15.1 percent below last year and 22 percent below the same point three years ago, when Atlantic City had taken in $3.5 billion.

Three years ago, there were 47,252 casino jobs in Atlantic City. Now there are 38,404.

"While some employees may be wavering, some are stronger," said Scott Smith, a 15-year dealer at Trump Plaza. "My choice is to be patient. The UAW is not going away. We want a contract for 100 percent of our workers, and we're not wrong to want that."